Using SimpleDateFormat to format date in Java

SimpleDateFormat date formatting class

Example 1: Date to String

y represents the year.
M represents the month.
d representative day
H stands for 24-decimal hours
h stands for 12-decimal hours
m stands for minutes
s stands for seconds.
S stands for milliseconds

package date;
  
import java.text.SimpleDateFormat;
import java.util.Date;
  
public class TestDate {
  
    public static void main(String[] args) {
          
        //y represents the year.
        //M represents the month.
        //d representative day
        //H stands for 24-decimal hours
        //h stands for 12-decimal hours
        //m stands for minutes
        //s stands for seconds.
        //S stands for milliseconds
        SimpleDateFormat sdf =new SimpleDateFormat("yyyy-MM-dd HH:mm:ss SSS" );
        Date d= new Date();
        String str = sdf.format(d);
        System.out.println("Current time passes yyyy-MM-dd HH:mm:ss SSS Formatted output: "+str);
         
        SimpleDateFormat sdf1 =new SimpleDateFormat("yyyy-MM-dd" );
        Date d1= new Date();
        String str1 = sdf1.format(d1);
        System.out.println("Current time passed yyyy-MM-dd Formatted output: "+str1);
         
    }
}

Example 2: String rotation date

The pattern (yyyyy/MM/dd HH: mm: ss) needs to be consistent with the string format, and if it is different, parse exceptions are thrown

package date;
  
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
  
public class TestDate {
  
    public static void main(String[] args) {
        SimpleDateFormat sdf =new SimpleDateFormat("yyyy/MM/dd HH:mm:ss" );
  
        String str = "2016/1/5 12:12:12";
          
        try {
            Date d = sdf.parse(str);
            System.out.printf("Character string %s Pass format  yyyy/MM/dd HH:mm:ss %n Converting to a date object: %s",str,d.toString());
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
          
    }
}

Practice: Date formatting

Prepare an array of dates with a length of 9
Initialize the array with random dates between 1970 and 2000
Sort the dates in ascending order according to their time
For example, 1988-1-21 12:33:22 will be ahead of 1978-4-21 19:07:23, because it takes less time, although the date is larger.

Answer:

package date;

import java.util.Date;
import java.util.Scanner;
import java.text.ParseException;
import java.text.SimpleDateFormat;

public class DateSort{
     //Random Date Generation Method
     public static Date getRandomDate(int start,int end){
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy");
            long timeStart=0;
            long timeEnd=0;
            try {
                Date dateStart = sdf.parse(String.valueOf(start));
                //System.out.println(dateStart);
                Date dateEnd = sdf.parse(String.valueOf(end));
                timeEnd = dateEnd.getTime()-1;
                timeStart = dateStart.getTime();
            } catch (ParseException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            long randomTime = (long)(timeStart+(Math.random()*(timeEnd-timeStart)));
            //System.out.println(randomTime);
            return new Date(randomTime);
     }
     //Formatting Output Date String Method
     public static String toString(Date d,String format){       
         SimpleDateFormat sdf = new SimpleDateFormat(format);
         return sdf.format(d);
         
     }
     public static void main(String[] args) {
         
            Date[] ds = new Date[9];  //Create random date arrays
            

//          Scanner s = new Scanner(System.in);
//          System.out.println("Please enter the year of commencement:");
//          int startYear = s.nextInt();
//          System.out.println("Please enter the year of end:");
//          int endYear = s.nextInt();
            
            for (int i = 0; i < ds.length; i++) {     //Initialize arrays
                ds[i] = getRandomDate(1900,2000);           
            }
            
            System.out.println("Random Date Array Before Sorting:");
            for (int i = 0; i < ds.length; i++) {
                System.out.print(toString(ds[i],"yyyy-MM-dd HH:mm:ss")+"\t");
                if(i%3==2)
                    System.out.println();
                
            }                  
                            
            for (int i = 0; i < ds.length; i++) {
                for (int j = 0; j < ds.length-1-i; j++) {
                    String str1 = DateSort.toString(ds[j],"HHmmss");
                    String str2 = toString(ds[j+1],"HHmmss");
                    
                    int j1 = Integer.parseInt(str1);
                    int j2 = Integer.parseInt(str2);
                    
                    if (j1>j2) {
                        Date temp = ds[j];
                        ds[j]=ds[j+1];
                        ds[j+1]=temp;                                
                        
                    }
                }
            }
            System.out.println("An array of sorted dates:");
            for (int i = 0; i < ds.length; i++) {
                System.out.print(toString(ds[i],"yyyy-MM-dd HH:mm:ss")+"\t");
                if(i%3==2)
                    System.out.println();
                
            }
     }
            
    
    
}